Field of the Disclosure
The present disclosure relates to an object tracking apparatus tracking an object included in images provided successively, a control method therefor, an image capture apparatus, a display apparatus, and a storage medium.
Description of the Related Art
A technique for extracting a particular object from images provided successively in a chronological order and tracking the extracted object is extremely useful, and is, for example, used for identifying the face region of a person and a person's body region in a motion picture. Such technique can be used in many fields, for example, a teleconference, a man machine interface, security, a monitor system for tracking any object, and image compression.
In digital still cameras and digital video cameras, Japanese Patent Application Laid-Open No. 2005-318554 and Japanese Patent Application Laid-Open No. 2001-60269 suggest a technique for extracting and tracking any object included in a captured image designated by using a touch panel or the like and optimizing a focus state and an exposure state for the object. For example, Japanese Patent Application Laid-Open No. 2005-318554 discusses an image capture apparatus for detecting (extracting) and tracking a position of a face included in a captured image and focusing and capturing an image of the face at an optimum exposure level. Japanese Patent Application Laid-Open No. 2001-60269 discusses a technique for automatically tracking a particular object by template matching. The template matching is a method for registering, as a template image, a partial image obtained by clipping an image region including a particular object to be tracked, and estimating, in the image, a region of which similarity to the template image is the highest or of which difference from the template image is lowest, so that the particular object is tracked. In the template matching, any given region included in the image is designated by using an input interface, such as a touch panel, and the template image is registered based on such region.
In the template matching, image data are used as an evaluation standard. In a case where there is a great change in appearance of the object, such as a change in the posture, between the template image and an image to be searched, there is an issue in which a correct region cannot be estimated.
For this issue, there is a method for using a histogram instead of image data itself as the evaluation standard of matching (histogram matching). By converting information indicating the object from the image data into the histogram, ambiguity is given, and an object tracking robust against the change in the posture of the object can be realized. On the other hand, when the histogram matching based on the histogram is compared with the template matching based on the image data, there is an aspect that the estimated accuracy of the position is inferior in a case where the change of appearance of the object is small.